Proper method for charging Kindle Touch Battery

[teasonc]

> #12
> a way to tell what percentage you are at

gasgauge-info -s

I use launchpad for this.

[teasonc]

I was able to drain Kindle DX Graphite to 64% (from 100% green-light-on type charge) in less than two hours, using text-to-speech at low volume, largest font size, most rapid speech rate.

The machine did not appear to enter sleep mode during the (unattended .. hooray) text-to-speech session.

For me, that completes the model of proper battery care for Kindle. My problem was being lazy about not catching it before a 100% full charge; if I can drain it down to a better storage level than 100%, I don't feel so bad about missing the exact time when I would rather have unplugged the charge cord (I like 80% here).

I try to shoot for 46% on a discharge curve, when doing this explicitly (as I've done here, using TTS as the workload the device is being asked to perform, so it's not just idling, sipping power at too conservative a rate to the purpose of draining it most rapidly).

I hit 64% this time; I'm okay with that. Much better than 100%, and I'll leave the device in plain sight, to remind me to try to get it closer to the mid 40 percentile, before zipping it away in its protective cover (to be forgotten for another 3 weeks as I enjoy my *other* Kindle .. whee).

Ymmv.

[germanor]

As a rule, no lithium-based battery should ever be allowed to fully discharge. Usually devices have circuitry to cut the device off before this happens, though. Li batteries work best and last longest with frequent shallow discharges and recharges, say allowing the device to go to 40% or so before recharging. Recharges don't need to be to 100%, either. LiON and LiPO batteries don't suffer from "memory" effects like Ni-based batteries. The old rules about fully discharging and fully recharging apply to nickel-based batteries--NiCd or NiMH (nickel-cadmium or nickel metal hydride), NOT to LiON or LiPO (lithium ion or lithium polymer). It is best to charge Li batteries often. Don't try to fully discharge the battery packs frequently. This only adds strain. Several partial discharges (regular use) with frequent recharges are better for LiON or LiPO than one total discharge.

[teasonc]

The real problem is that proper operation of the cells has to be supervised by a human, in real time. You have to notice (humanly) that it's at 40% (time to recharge) and get there before it crests 80% (risk of overcharge) -- except for a (say) bi-monthly calibration cycle (see earlier in this thread).

The manufacturers are making it difficult to do what is known to be best for the batteries, from an operational standpoint.

[JonathanH]

Most importantly, you also have to figure out whether all this is worth your time. For example, I've learned to be pretty relaxed about charging: I tend to charge my Kindle Touch when it gets down to 25% or so (eyeballing from the gauge), and unplug it again when I notice the charging LED has switched from amber to green. So I'm doing 25%-100% cycles, instead of teasonc's 40%-80%.

Maybe as a result of this my Kindle's battery will "only" last 600 charging cycles, whereas teasonc's will last many more (shorter) charging cycles. Since I charge every couple of weeks, that means mine will "only" last for.. let's see... about 24 years. By which point I'm expecting to be reading on something bigger, lighter, and cheaper anyway. And if I'm actually still using it then, I'll have saved myself 600 instances of worrying about the "optimal" charging cycle. A bargain!

[There are many caveats here. A 24-year-old battery will degrade just from being old. I plucked the number 600 from out of a hat, but 500-1000 cycles is a good guess. A lot depends on Amazon's battery calibration parameters, which we can't change - cf the current story that the iPad3's parameters are buggy, and its "100%" figure is actually set too low]

Edit: I think we can come up with a reasonable rule of thumb here. That is, you should only worry about this stuff if you use your Kindle so much that you have to charge it more than once a week. If that doesn't apply to you, then don't worry, because your battery will die of old age (10 years) before it it dies of too many charging cycles (500-1000 cycles).

[teasonc]

This guy's battery rant is a bit uneven, but hits most of the essential talking points:

http://www.primecell.com/qli-Ion.htm

...you realize - when you own a Li-Ion battery - keeping it alive and well - is similar to owning a work horse.

You must never feed it too much or it will not want to work.

You must always feed it something or it will get weak and die.

You must make it work nearly every day - or it will get lazy and not want to work.

You must never work it too hard before you feed it - or you may kill it.

I'm not sure which points he makes I agree with strongly, but the italicized one ('nearly every day') is the one I think about the most.

[geoffwood]

Honestly, i don't see what the fuss is about. My Laptop batteries see FAR more use than my kindle and with no particular attention paid they both have over 500 full cycles and are still at 95% plus of their original capacity.

With a Kindle battery, even if I read a LOT I might get through one charge cycle a week, but more likely one per month, so we are looking at a life expectancy of somewhere between 10 and 40 years. I really don't see the point in sweating the details to try and get an extra 10% of life out of a battery that will already far out live the useful life of the Kindle.

[HarryT]

Originally Posted by geoffwood

With a Kindle battery, even if I read a LOT I might get through one charge cycle a week, but more likely one per month, so we are looking at a life expectancy of somewhere between 10 and 40 years. I really don't see the point in sweating the details to try and get an extra 10% of life out of a battery that will already far out live the useful life of the Kindle.

A typical lithium ion battery has a life expectancy of around 5 years. The clock starts ticking when the battery is first charged, and nothing will halt it.

As you very rightly say, for an eInk reading device the battery life is purely determined by this physical lifetime of the battery, and not on how you choose to charge it.

[geoffwood]

Originally Posted by HarryT

A typical lithium ion battery has a life expectancy of around 5 years. The clock starts ticking when the battery is first charged, and nothing will halt it.

Interesting, I wasn't aware of that and as you say it makes the charging debate a moot point

[HarryT]

Originally Posted by geoffwood

Interesting, I wasn't aware of that and as you say it makes the charging debate a moot point

Exactly. For something like a phone, where you might well be charging it every day, proper charging protocols can usefully extend the battery life. For an eInk reader, it's completely irrelevant.